Racing's ruling body has been forced into a review of its approach to testing jockeys for alcohol after the embarrassing discovery that its equipment is not as accurate as previously believed. The revelation was made during a disciplinary hearing on Thursday involving the rider Franny Norton, who ended up with a 16-day ban when he had been facing a much longer suspension.

Tested at Salisbury on 7 September, Norton's breath was found to contain alcohol in a concentration of 35 micrograms per 100 millilitres, right on the threshold for an "upper level" finding under the British Horseracing Authority's regulations. But Norton fielded an expert witness to point out that the equipment involved, the Lion Alcometer SD-40, has "a scientifically established margin of error" in the region of 10% which the BHA has never applied to test results taken from jockeys.

This would have been Norton's second upper-level positive within two years, triggering a suspension with an entry point of 100 days. Instead, the BHA's disciplinary panel downgraded the result to lower-level and imposed the shorter ban.

Norton's representatives pointed out that his previous test positive was also within the margin of error and argued that he should therefore have had a much shorter ban than the 40 days which he served for it. For that reason, they contended, he should face no punishment on this occasion, but the panel dismissed that argument.

The BHA immediately announced a review of its policies in this area and insisted that there were no other cases from the past which might have to be revisited in light of the discovery. "We had no reason to suspect the equipment was anything other than accurate," said Robin Mounsey, the BHA's spokesman.

The panel's full reasons for its decision will be published, probably next week.